Engine starter



March 14, 1944. w rrz GERALD 2,343,966

ENGINE STARTER Filed April 10, 1942 2 Sheets-Sheet 1 LJZDZTZ'L 1/1 EZZ Gerald March 14, 1944. J. w. FITZ GERALD ENGINE STARTER Filed April 10, 1942 2 Sheets-Sheet 2 59% 1. 01121 I KFz zz Gerald him Patented Mar. 14, 1944 2,343,966 ENGINE STARTER John W. Fitz Gerald, Milwaukee, Wis., assigncr to Briggs & Stratton Corporation, Milwaukee, Wis.,.a corporation of Delaware Application April 10, 1942, Serial No. 438,462

. 9 Claims.

This invention relates to engine starters of the type wherein the drive pinion is automatically propelled to and from mesh with the engine ring gear. V

In general it has been found that the ideal construction for starters of this type comprises a driving head adapted to be secured to the shaft of the starter motor, an actuating member loosely mounted on the motor shaft or a sleeve slipped thereon and carried by the driving head, and a tubular extension on the pinion threaded fonto the actuating member.

By virtue of the threaded connection between the actuating member and the pinion sleeve or extension, relative rotation between these parts effects longitudinal motion of one with respect to the other, depending upon the direction of relative rotation. Hence, by transmitting torque from the drive head to the actuating member the desired translation of the pinion along the shaft is accomplished, such movement of the pinion being limited by a suitable stop upon attainment of full meshing relationship. t I

The parts thus far described and operatingjin the manner stated, accomplish the desired translation of the pinion along the shaft to and from mesh with the ring gear, but yieldability must be incorporated to cushion the application of the engine load on the starter motor and also to accommodate occasional collision .of the teeth on the starter pinion with those of the ring gear.

The means by which this necessary yieldability has been incorporated in starters in the past has taken many different forms.

In some instances the yieldable means has been intenpositioned between the pinion and the actuating member, but most generally and practically, it constituted the driving connection between the actuating member and the drive head which is fixed to the motor shaft i In the early type starters yieldability was obtained through the use of a coiled spring which combined torsional and endwise resiliency. Inasmuch as the torque had to be transmitted throu h the spring its crystallization and the consequent failure of the starter was a common occurrence; A vast improvement over the early type starter was obtained through substitution of a rubber collar as the yieldable driving connection between the actuating member and. the drive head, as

evidenced by Patent No. Re. 20,686, dated April The use of rubber as the yieldable driving connection not only eliminated the objection of failure due to crystallization of the spring, but it produced a much quieter starter.

However, with the increasing difiiculty of obtaining rubber, either natural or synthetic, further revision of starters of this type must be made, and it is therefore an object of this invention to provide an engine starter which retains all the desirable constructional characteristics of past startersbut utilizes an entirely new manner of obtaining the necessary yieldability which, though it incorporates the use of a spring and eliminates the need for rubber, is free from the objections inherent in the earlier use of springs.

In general this invention achieves this result through the use of a yieldable driving connection between the actuating member and the drive head formed conjointly by a compression spring which carries none of the driving torque and a novel torque transmitting cam connection arranged to reduce the load on the spring.

Another object of this invention resides in the provision of a novel yieldable driving connection for starters of the character described which is so designed that any desired gradient of resistance to endwise thrust imparted to the actuating member may be built into the starter.

Still another object of this invention is to provide means for insuring quietness in operation by yieldingly maintaining the cam surfaces on the actuating member and drive head engaged at all times.

With the above and other objects in view, which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims. The accompanying drawings illustrate several complete examples of the physical embodiment of the invention constructed according to the best modes so far devised for the practical application of the principlesthereof, and in which:

Figure 1 Ba side view of a' starter embodying this invention, "with parts thereof broken away and in section and showing the pinion in its retracted "inactive position;

Figure 2 is a view similar to Figure l but showing the pinion advanced into mesh with the ring gear;

Figure 3 is a perspective view of the drive head unit; 7 I I be balanced between them to obtain any desired gradient of resistance to end thrust;

Figure 8 is a perspective view oi the irivehead f unit of the starter construction shown in Figure.

Figure 9 is a perspective View of the actuating member construction employed in the starter shown in Figure '7. T f

Referring now more particularly to the accomp'anying drawings, in which like numerals indi cate like parts, the numeral 5' designates the ring gear of an engine to be started and with which the pinion 6 of the starter meshes during the starting cycle. I a

The pinion 6 has a rearwardly extending sleeve or tubular extension I internally threaded to fit the threads '8 of an actuating member 9. The actuating member comprises, a flange it having a forwardly directed tubular extension H on which the threads 8 are formed and a rearward ly directed cylindrical projection l2. This rearwardly directed cylindrical projection I2 is stepped to provide diametrically opposite narrow and wide po tions I3 and M.

One endof the wide portion, {4 terminates in an abrupt step parallel with the axis of the actuator, but at its opposite end an inclined cam surface !5 constitutes the step between the two portions 13: and, I4; This inclined cam surface it cooperates with a correspondingly inclined cam surface I! on a drive head indicated generally by the numeral l8.

The drive head [8 comprises a sleeve is te le-. scoped over the shaft 20, ofthe starter motor and a boss 2| fixed to the sleeve. screw connection locks the drive head to, the motor shaft. V

Carried, by the boss 2| and projecting radially therefrom is an annular flange 22. This, flange 22 is of the same diameter as the cylindrical extension l2 on the actuating member and projecting forwardly therefrom is a cylindrical ex tension 23 complementary inshape to the extension I2, that is, it is stepped and has. narrow and wide portions 24 and 25, respectively.

One junction between these portions is formed by the inclined cam surface I] and its opposite junction is in the form, of a, square shoulder or step 25. This shoulder 2.6, however, is angularly or circumferentially displaced from the shoulder l5 when the actuatingflmember is assembled with the drive head and the cam surfaces 16. and. l 7 are in engagement, as shown in Figure 5.

This clearance is provided to. insure unhindered functioning of the cam connection.

Interpose'd between the-flanges of the actuate ingfmember and drive: head is a compression spring 2! which yieldingly holds the actuating member longitudinally away fromthe drive head,

and, to limit the movement apart of these ele- V ments under influence of the spring, a retaining shell28 isapplicd ver the. flanges of, theact'iiat ing member and drive head. This'shell has-an inwardly directed flange 29 engaging behind the A suitable key and,

drive head isformed; as a. curve. and pertain a. decrea in ncrem nt. it fo low flange of the drive head and has a bead 30 rolled over the edge of the flange In on the actuating member.

Thus, it will be seen that rearward longitudinal displacement of the actuating member produced by the action of the screw and resulting either from collision of the pinion teeth with the teeth of the ring gear or the, picking up of the engine load when the pinion is in its forward limit of movement defined by a stop 3| on the front end of the sleeve [9 is resisted jointly by the compression spring 2'1 and the force of friction resulting from the cam connection.

In this manner it is possible to utilize a compression spring to. take the end thrust and substantially duplicate'the resiliency of a rubber collar. Tests having shown that it is impossible to obtain a spring capable of installation in the space available which of itself could duplicate the action of a rubber collar as employed in starters of the type, described in the aforesaid Fitz Gerald patent; but with the cam connection frictionally resisting end thrust the load on the spring is materially lessened. It is thus feasible to use a relatively light coilspring, especially as none of the driving torque is carried by the spring. The entire torque is transmitted by the cam connection.

This construction achieves all of the required yieldability in a starter as the torsional resiliency necessary to cushion the application of the engine load to the starter motor is obtaineclthrough the translation by the screw of torque loadfi-nto rearward endwise displacement of the actuating member, which, of course, is cushioned; I 3

When the engine starts the-actuating member isapt to be rotated with respect to the drive head to disengage the camsurface's and-engage the abrupt shoulders IE-"and 26. While this action would in nowise affect the operation of the starter, it would result in an objectionable clicking sound and might increase wear onthef cam surfaces due to the hammerblow resulting-from taking up the lostmotion when the starter again functioned. T

Hence, it is desirable to incorporate means'for holding the cam surfaces ,yield'ably inengage! ment. This is conveniently accomplished by means of the spring 21 merely by forming. pro.- jections 32- on the ends of the. spring and engaging the samein appropriate, recessesiin the drivethead and actuating: member. as. clearly showninFigure 6. I- V:

With the constructionshown .in Figures 1V to 6, inclusive, the, cam ,,surfa.ces,are arranged at the same angle (3.0? in his-instaccelthrqu h: out, their entire len th, ut by chan ngthe shape of the cam surfaces it. isnossible to obta n y s ed pr ression oi resist nce to end thrust on the actuating member, and-in. Figures '7 o 9, inclusive, one manner or effecticea his 11esult, is illustrated V v As here shown, the can; suriace; t1"

surface d of: thea tuatiu'c. member. mere y a rounded projection. arrangedyqtoz rider n. the curved sur ace ll. Inasmuch; tlie unvex a ls awayi rom the hi h po nt. of th. 'cantw th s ancer c r a a d s l cem n eith a t, ating member is initially light, being earrmarily by the spring, but increases as the; on the starter builds up.

. .Obviousl-y, any desired shape of cam maybe employed to produceany desired action.

From the foregoing description, taken in conhection'withthe accompanying drawings, it will be readily apparent to those skilled in the art hat this invention provides a starter which re- I tains the desirable attributes of starters using tuator and the power shaft comprising opposed;

abutments on the actuator and the power shaft, said abutments being relatively movable rotarily and axially with respectjto each other; yieldable means interposed between said abutments to yieldingly resist motion of the same toward'each other under the influence of rearward end'thrust on the actuator; and a torque transmitting connection. between said abutments comprising a cam connection operable to simultaneously transmit torque and yieldingly frictionally resists relative endwise movement of said abutments toward each other brought about by rearward end thrust on the actuator to thereby aid the yieldable means in resisting such rearward end thrust.

2. An engine starter of the type wherein a pinion member is automatically propelled forwardly into mesh with the ring gear of an engine to be started by means of an actuator driven from a power shaft and having a threaded connection with the pinion member, and wherein rearward end thrust is imposed upon the actuator upon operation of the starter both prior to and during meshing of the pinion member with the ring gear, said starter being characterized by: the provision of a longitudinally yieldable driving connection between the actuator the objections inherent in and the power shaft formed conjointly by cam means arranged to transmit torque from the power shaft to the actuator and at the same time yieldingly frictionally resist endwise movement of the actuator under the influence of rearward end thrust thereon, and a compression spring also yieldingly resisting endwise movement of the actuator brought about by rearward end thrust on the actuator.

3. In an engine starter of the type wherein a pinion member is automatically propelled into and out of mesh with an engine ring gear by means of an actuating member connected with the pinion member in a manner to effect forward propulsion of the pinion member into mesh with the ring gear during rotation of a power shaft, and wherein operation of the starter imposes rearward end thrust on the actuating member; an endwise resilient driving connection between the power shaft and the actuating member formed conjointly by a compression spring confined between opposed abutments on the power shaft and actuating member so as to yieldingly oppose rearward end thrust on the actuating member, and engaging cam surfaces on the power shaft and actuating member arranged to transmit torque and also to yieldingly resist relative movement of the abutments toward each other .and a pinion m'ember under the influence of rearward end thrust onthe actuating member. n

4. In an engine starter having a power shaft movable longitudinally alongand ro'tatably with the power shaft, said engine starter including an actuator driven from the power shaft and connected with the pinion member to automatically propel the pinion forwardly into operative relation with the engine during starting of the engine and to automati cally retract the pinion upon starting of the en gine: a part fixed onthe power shaft;' a part on the actuator inf juxtaposition to said part on the power shaft; radial abutments on said parts engaging totransmit torque from the powershaft to the actuator, at least'one of said abutments having a spiralcam formation so that the engageme'nt ofthe' said abutments frictionally op poses endwise movement thereof toward each other with a force depending upon the shape of said spiral cam formation; yieldable means interposed between said parts on the power shaft and actuator yieldingly resisting endwise movement of said parts toward each other so that said yieldable means in conjunction with said spiral cam connection yieldingly opposes endwise retraction ofthe a'ctuatorfand means for limiting endwise movement of said parts awa from' each other.

5. In an engine starter of the type wherein a pinion member is automatically propelled along a power shaft by means of an actuating member connected with the pinion member in a manner to effect propulsion of the pinion member to and from mesh with the ring gear: cooperating abutments on the actuating member and the power shaft engaging to transmit torque from the shaft to the actuating member, at least one of said abutments having its surface which engages the other abutment spirally arranged about the axis of the shaft so that while engagement of said abutments transmits torque it also yieldingly frictionally resists endwise movement of the actuating member toward the abutment on the shaft; and a spring yieldingly urging the actuating member in an endwise direction away from the abutment on the shaft, so that said spring coacts with the frictional resistance to said endwise movement of the actuating member to provide endwise resiliency in the torque transmitting connection between the shaft and actuating member.

6. In an engine starter of the type wherein a pinion member is automatically propelled along a power shaft by means of an actuating member connected with the pinion member in a manner to effect propulsion of the pinion member to and from mesh with the ring gear: cooperating abutments on the actuating member and the power shaft engaging to transmit torque from the shaft to the actuating member, at least one of said abutments having its surface which engages the other abutment spirally arranged about the axis of the shaft so that while engagement of said abutments transmits torque it also yieldingly frictionally resists endwise movement of the actuating member toward the abutment on the shaft;

and a spring yieldingly urging the actuating member in an endwise direction away from the abutment on the shaft, so that said spring coacts with the frictional resistance to said endwise movement Of the actuating member to provide endwise resiliency in the torque transmitting connection between the shaft and actuating member, and the spiral of said abutment decreasing in pitch so that the frictional resistance to end thrust on the actuator is progressively greater as a n c m part on elm-aim 1.

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\ 9. In .anengine starter of .the charaot'er described; I substantially; coaxial rotatable driving and driven. 'na'embersf'bhe driven member being movable axially toward the driving, member as a regult of end thrust imposed on t h driven memhere during th transmission of driving, torque between said members, and an endwise yielclable driving connection between said'inembers comprising cooperating cam parts thereonengaging to simultaneously transmit torque between the members, and to frictionally yieldaxiaHy under theiinpositionof end thrust on the driyen'mem her, and a spring urging said membersjapart' and cooperating with the cam pa-rtsvto aid in absorbing end bhru st on th driven member.

JOHNW; FITZ G RA D 

